20160226 I 680 Corridor Study Appendix D
SANTA CLARA COUNTY
I-680 CORRIDOR STUDY
APPENDIX D TRAFFIC OPERATIONS ASSESSMENT MATERIAL
HMH ENGINEERS - FEHR & PEERS - PARSONS BRINKERHOFF - DAVID J. POWERS & ASSOC.
February 26, 2016
The Delay Reduction Index (DRI) was used to perform a quantitative evaluation of select highway category improvements for the Mobility Effects section of the evaluation process. Using demand volume data from the VTA travel demand model and the MTC model delay curve equation (delay increases as volume-tocapacity ratio increases), Fehr & Peers estimated the total person-hours of delay on each I-680 freeway segment between US 101 and the Alameda County-Santa Clara County line. This calculation used assumed lane capacities for various freeway lane types (general purpose, auxiliary, and preferential lanes), assumed average vehicle occupancies, free flow travel times and segment length to determine the estimated personhours of delay on the segment. Year 2040 baseline volumes were developed by extrapolating between Base Year (2013) and Year 2020 volumes, or by increasing volumes at a ½ percent per year (linear) growth factor, whichever was greater. Based on the description of the improvement to be tested the calculation was modified to reflect impacts to lane capacities. Then, it was compared to the baseline calculation to estimate the change in personhours of delay due to the improvement or DRI. A decrease in person-hours of delay results in a positive DRI. For example, an improvement that added an express lane for a significant portion of the corridor would be expected to increase the delay reduction index more significantly than one that converted an existing lane to an express lane. Improvements evaluated under the DRI method were given Mobility Effects score using the following criteria: Score 5 4 3 2 1 0
DRI Range >10,000 5,000-10,000 1,000-5,000 100-1,000 0-100
I-680 CORRIDOR STUDY
APPENDIX D TRAFFIC OPERATIONS ASSESSMENT MATERIAL
HMH ENGINEERS - FEHR & PEERS - PARSONS BRINKERHOFF - DAVID J. POWERS & ASSOC.
February 26, 2016
The Delay Reduction Index (DRI) was used to perform a quantitative evaluation of select highway category improvements for the Mobility Effects section of the evaluation process. Using demand volume data from the VTA travel demand model and the MTC model delay curve equation (delay increases as volume-tocapacity ratio increases), Fehr & Peers estimated the total person-hours of delay on each I-680 freeway segment between US 101 and the Alameda County-Santa Clara County line. This calculation used assumed lane capacities for various freeway lane types (general purpose, auxiliary, and preferential lanes), assumed average vehicle occupancies, free flow travel times and segment length to determine the estimated personhours of delay on the segment. Year 2040 baseline volumes were developed by extrapolating between Base Year (2013) and Year 2020 volumes, or by increasing volumes at a ½ percent per year (linear) growth factor, whichever was greater. Based on the description of the improvement to be tested the calculation was modified to reflect impacts to lane capacities. Then, it was compared to the baseline calculation to estimate the change in personhours of delay due to the improvement or DRI. A decrease in person-hours of delay results in a positive DRI. For example, an improvement that added an express lane for a significant portion of the corridor would be expected to increase the delay reduction index more significantly than one that converted an existing lane to an express lane. Improvements evaluated under the DRI method were given Mobility Effects score using the following criteria: Score 5 4 3 2 1 0
DRI Range >10,000 5,000-10,000 1,000-5,000 100-1,000 0-100
